The overall goal of this research is to understand how emotional communication, especially that between mother and infant, serves to regulate interpersonal behavior. The thrust of this research is to develop a knowledge base from which the nurse can draw in order to provide health care that will enhance optimum infant behavior and development. The conceptual base for this work is that of social referencing--the process whereby individuals (in this case infants) seek out, or otherwise attend to, and use the emotional information from another person as a basis for determining their own response to the situation. The 3 specific aims of this research will address the behavior regulatory role of emotional communication conveyed by the voice. The first will focus on determining the developmental onset of the infant's ability to use vocal emotion as a guide for behavior. Five- and 8 1/2-month-olds will hear the mother sound happy or angry as they reach for a nearby object. Dependent measures include reaching and touching the object, facial and vocal expressions, and looking to the mother. It is expected that 5-month-olds will not be able to act appropriately to the mother's signals. The second aim will address whether self-produced locomotion is a mediator of behavior regulation to the voice in that by crawling about and learning features of the environment the infant may be better able to make the connection between the mother's emotional expression and the target of that expression. Locomotor and prelocomotor infants at 7 1/2 months of age will be subjects using the procedure and behavioral measures described above. The third aim will focus on whether infants are better able to use emotional signals to guide behavior if signals are presented in multi-channel (face and voice) rather than single channel (voice alone) fashion. Ten-month-old infants will hear and see a happy, frightened, or angry mother as a result of their behavior, for example, knocking over a canister of styrofoam packing discs. Of special interest is whether infants respond differently to the negative emotions. Dependent measures include crawling to the mother, clinging to the mother, crawling away from the mother and toy to a different location, affective tone of facial expressions and vocalizations. This line of research will lay the foundation for exploring the infant's use of signals in stressful clinical situations, for instance, during a physical examination or during a hospital stay.